Floodplain development approval required. No use, development or activity may occur in frequently flooded areas except as specifically allowed by this part. All use, development or activity which is allowed is subject to the performance standards of this section and shall not result in a rise in the BFE. The requirements of this section may only be modified through a Variance.
A. Review of Proposed Development – Applicable Process.
1. Critical Areas Land Use Permit. Proposals for development in frequently flooded areas shall require a Critical Areas Land Use Permit, Part 20.30P LUC. The Director shall determine that the requirements of this chapter have been satisfied; all necessary permits have been obtained from federal, state, or local agencies prior to approval; the site is reasonably safe from flooding, and the proposed development is not located in the floodway, or if located in the floodway, the development complies with the provisions of this chapter. The Director shall notify FEMA when annexations occur in frequently flooded areas.
2. Variance to the Frequently Flooded Areas Provisions.
a. Applications to modify the requirements of this section shall require a Variance Permit, Part 20.30G. The Director may approve or approve with modifications an application for a Variance from the requirements of this section as set forth in LUC 20.30G.140.
b. All Variance records, including justification for approvals, shall be maintained in accordance with the City of Bellevue record retention policy. Upon approval of a Variance, the Director shall notify the applicant in writing the following:
i. That the issuance of a Variance to construct below the base flood elevation (BFE) will result in increased premium rates for flood insurance up to amounts as high as $25.00 per $100.00 of insurance coverage; and
ii. That such construction below the BFE increases risks to life and property.
3. Review of Development. Where elevation data is not available, either through the FIS, FIRM, or as provided in LUC 20.25H.175, applications for development in frequently flooded areas shall be reviewed to assure that development will be reasonably safe from flooding. The test of reasonableness is a local judgement, which includes, but is not limited to, the use of historical data, high water marks, and photographs of past flooding where available.
B. General Performance Standards. Where use or development is allowed pursuant to LUC 20.25H.055, the following general performance standards apply, in addition to the applicable performance standards in subsection C of this section:
b. The intrusion is at an elevation and orientation which maintains the existing vegetation of the frequently flooded area in a healthy condition. Solar access to vegetation must be maintained at least 50 percent of daylight hours during the normal growing season; and
Development not meeting the requirements of subsection B.1 of this section may be allowed pursuant to LUC 20.25H.055 and only in accordance with the requirements set forth in the remainder of subsection B of this section.
2. Elevation Certificate Following Construction. Following construction of a structure within a frequently flooded area, where the base flood elevation is provided, the applicant shall obtain an elevation certificate. The elevation certificate shall be completed by a surveyor licensed in the State of Washington and shall be submitted to City of Bellevue, Utilities Department. The Director shall obtain and transmit to the Director of the Utilities Department the elevation in relation to North American vertical datum (NAVD 88) of the lowest floor, including basement, and attendant utilities of a new or substantially improved structure permitted by this part. All records shall be maintained for public inspection in accordance with 44 C.F.R. 60.3(b)(5)(iii).
3. Construction Materials and Methods.
a. Site Design. All structures, utilities, and other improvements shall be located on the buildable portion of the site out of the frequently flooded area unless there is no buildable site out of the frequently flooded area. For sites with no buildable area out of the frequently flooded area, structures, utilities, and other improvements shall be placed on the highest land on the site, outside of the floodway, oriented parallel to flow rather than perpendicular, and sited as far from the stream and other critical areas as possible. If the Director detects any evidence of active hyporheic exchange on a site, the development shall be located to minimize disruption of such exchange.
b. Methods That Minimize Flood Damage.
ii. Building Mechanical Equipment. Unless otherwise specified in subsection C of this section, mechanical equipment, including but not limited to electrical, heating, ventilation, plumbing, air conditioning, and other service facilities, shall be dry floodproofed or elevated one foot or more above the BFE.
c. Utility Protection. Water wells shall be located on high ground that is not in the floodway; new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters; and on-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
i. All new construction and substantial improvements, including those related to manufactured homes, shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy.
ii. All manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors.
e. Enclosed Area Below the Lowest Floor. When buildings, including manufactured homes, are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage.
a. Post and Pile. Post and piling techniques are preferred and are presumed to produce no increase in the BFE so long as only posts or piles are located below the BFE. Demonstration of no net rise in the BFE through calculation is not required.
b. Compensatory Storage. Proposals using compensatory storage techniques to assure no rise in the BFE shall demonstrate no net rise in the BFE through the calculation by accepted engineering practice or methods established in the Utilities Storm and Surface Water Engineering Standards, Section D4-05.5, Floodplain/Floodway Analysis, whichever is more restrictive, now or as hereafter amended.
5. Development in the Regulatory Floodway.
a. Encroachment into Regulatory Floodway Prohibited. A residential structure located partially within the regulatory floodway will be considered as totally within the regulatory floodway and must comply with this subsection B.5. Encroachments, including but not limited to fill, new construction, substantial improvements, and other development, are prohibited, unless a registered professional engineer certifies that the proposed encroachment into the regulatory floodway shall not result in any rise in the BFE using hydrological and hydraulic analysis performed in accordance with accepted engineering practice or City of Bellevue Storm and Surface Water Engineering Standards, whichever is more restrictive. All new construction and substantial improvements shall comply with this section.
ii. Repairs, reconstruction, or improvements to a structure, the cost of which do not exceed 50 percent of the market value of the structure either (1) before the repair, reconstruction, or improvement is begun, or (2) if the structure has been damaged, and is being restored, before the damage occurred. Work done to comply with state or local health, sanitary, or safety codes identified by the Building Official and which are the minimum necessary to assure safe living conditions or any alteration of a Historic Structure shall not be included in the 50 percent market value determination.
c. Substantially Damaged Residential Structures.
i. The Director may request the Washington State Department of Ecology to assess the risk of harm to life and property posed by the specific conditions of the regulatory floodway, and provide the City with a recommendation on repair or replacement of a substantially damaged residential structure consistent with WAC 173-158-076, now or as hereafter amended. Property owners shall be responsible for submitting to the City any information necessary to complete the assessment when such information is not otherwise available. No repair or replacement of a substantially damaged residential structure located in the regulatory floodway is allowed without a recommendation from the Department of Ecology.
ii. Before the repair, replacement, or reconstruction is started, all requirements of this section must be satisfied. In addition, the following conditions shall be met:
(5) New and replacement water supply systems are designed to eliminate or minimize infiltration of flood water into the system;
(6) New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and
(7) All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.
a. Modifications shall only be allowed in accordance with the habitat improvement projects.
b. Modification projects shall not result in blockage of side channels.
c. The City of Bellevue shall notify adjacent communities, the state departments of Ecology and Fish and Wildlife, and the Federal Insurance Administration about the proposed modification at least 30 days prior to permit issuance.
d. The applicant shall maintain the altered or relocated portion of the stream channel to ensure that the flood-carrying capacity is not diminished. Maintenance shall be bonded for a period of five years, and be in accordance with an approved maintenance program.
7. Compensatory Storage. Development proposals must not reduce the effective base flood storage volume of the area of special flood hazard. Grading or other activity that would reduce the effective storage volume must be mitigated by creating compensatory storage on the site. The compensatory storage must:
a. Provide equivalent elevations to that being displaced;
b. Be hydraulically connected to the source of flooding;
c. Be provided in the same construction season and before the flood season begins on September 30th;
e. Be supported by a detailed hydraulic analysis that:
i. Is prepared by a licensed engineer;
ii. Demonstrates that the proposed compensatory storage does not adversely affect the BFE; and
f. Meet all other critical areas rules subject to this part. If modification to a critical area or critical area buffer is required to complete the compensatory storage requirement, such modification shall be mitigated pursuant to an approved mitigation and restoration plan, LUC 20.25H.210.
8. Floodplain Ecological Functions. The use or development shall meet National Flood Insurance Program requirements for the protection of floodplain ecological functions in accordance with guidelines established by the Director. Floodplain ecological functions include, but are not limited to, stormwater quality, floodwater storage and conveyance capacity, and habitat.
9. Development Containing 50 Lots or 5 Acres. Where detailed base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain either 50 lots or involve 5 acres, regardless of the number of lots.
C. Specific Performance Standards. In all areas of special flood hazards where BFE data has been provided as set forth in LUC 20.25H.175.A and where use or development is allowed pursuant to LUC 20.25H.055, the following specific performance standards apply:
1. New Residential Construction, Modification of Existing Development, and Existing Nonconforming Development. New construction, lateral additions, and substantial improvements to existing development and existing nonconforming development is allowed only through a reasonable use exception, LUC 20.25H.190.
a. Residential construction (single-family and multifamily dwellings), including new construction, substantial improvements, or reconstruction due to substantial damage. New Construction, Substantial Improvements, and reconstruction due to substantial damage of any residential structure shall have the lowest floor, including basement, elevated one foot or more above the base flood elevation (BFE). Mechanical equipment and utilities, including but not limited to electrical, heating, ventilation, plumbing, air-conditioning, and other service facilities, shall be elevated one foot or more above the BFE. In an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the Highest Adjacent Grade. Fully enclosed areas below the BFE that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:
i. A minimum of two openings having a total net area of not less than one square inch for every one square foot of enclosed area subject to flooding shall be provided.
ii. The bottom of all openings shall be no higher than one foot above grade.
iii. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters.
2. Repair and Maintenance of Existing Parks and Park Facilities – New or Expanded City and Public Parks. Substantial improvement of any structure in frequently flooded areas must comply with the nonresidential performance standards found in this section.
3. New or Expanded Essential Public Facilities.
a. The facility must be constructed in conformance with the residential and nonresidential construction standards of this subsection and be elevated to at least one foot above the BFE or in compliance with ASCE 24, whichever is more restrictive.
4. New or Expanded Public Rights-of-Way, Private Roads, Access Easements and Driveways.
5. Changes to the Frequently Flooded Areas. If a project will alter the BFE or boundaries of the Special Flood Hazard Area (SFHA), then the project proponent shall provide the City with engineering documentation and analysis regarding the proposed change. If the change to the BFE or boundaries of the SFHA would normally require a Letter of Map Change, then the project proponent shall initiate, and receive approval of, a Conditional Letter of Map Revision (CLOMR) prior to approval of the development permit. The project shall be constructed in a manner consistent with the approved CLOMR.
If a CLOMR application is made, then the project proponent shall also supply the full CLOMR documentation package to the Director to be attached to the floodplain development permit, including all required property owner notifications.
6. Recreational Vehicles. Recreational vehicles are required to either:
a. Be on the site for fewer than 180 consecutive days; and
b. Be fully licensed and ready for highway use on its wheels or jacking system, be attached to the site only by quick-disconnect-type utilities and security devices, and have no permanently attached additions; or
7. Manufactured Homes. All manufactured homes to be placed or substantially improved or reconstructed due to substantial damage on sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot or more above the BFE. Mechanical equipment and utilities, including but not limited to electrical, heating, ventilation, plumbing, air-conditioning, and other service facilities, shall be elevated one foot or more above the BFE. All manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors.
8. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall meet the requirements of either subsection C.8.a or C.8.b of this section.
a. In AE and A1-30 zones or other A-zoned areas where the BFE has been determined or can be reasonably obtained new construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall:
i. Have the lowest floor, including basement, elevated one foot or more above the BFE, or elevated as required by ASCE 24, whichever is greater. Mechanical equipment and utilities shall be waterproofed or elevated one foot or more above the BFE, or as required by ASCE 24, whichever is greater; and
ii. If located in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding, but in all cases the lowest floor shall be two feet above the Highest Adjacent Grade.
i. Be dry floodproofed so that below one foot or more above the BFE the structure is watertight with walls substantially impermeable to the passage of water or dry floodproofed to the elevation required by ASCE 24, whichever is greater;
ii. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
iii. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications, and plans. Such certification shall be provided to the Development Services Department. Following construction of the structure, elevation certificates shall be submitted to the City that record the actual (as-built) elevation to which the structure was floodproofed. The City shall notify the applicant that insurance premiums will be based on rates that are one foot below the floodproofed level, and floodproofing the building an additional foot will reduce insurance premiums.
c. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or fully enclosed areas below the BFE that are not floodproofed shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect, or must meet or exceed the following minimum criteria:
i. A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided;
ii. The bottom of all openings shall be no higher than one foot above grade;
iii. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters; and
d. Lateral Additions. Lateral additions to structures that qualify as a substantial improvement must meet the elevation standards of new nonresidential construction. If the common wall between the lateral addition and the existing structure is demolished as part of the project, then the entire structure must meet the standards of new, nonresidential construction.
e. Pre-FIRM Buildings. Pre-FIRM buildings that qualify as a substantial improvement (including lateral additions) must meet the elevation standards of new construction. (Ord. 6521, 7-27-20, § 7; Ord. 6417, 5-21-18, § 44; Ord. 6013, 8-1-11, § 3; Ord. 5680, 6-26-06, § 3)